1. Field of the Invention
The present invention relates to a thin film magnetic head suitable for writing information in or reading recorded information from a magnetic recording medium, such as a hard disk.
2. Description of the Prior Art
The magnetic film and conductive coils of the magnetic circuit of a thin film magnetic head, in general, are formed by vacuum thin film forming techniques. Accordingly, the thin film magnetic head has a narrow magnetic gap which can readily be formed and is capable of dealing with very narrow tracks, high-resolution recording and high-density recording.
Generally the magnetic circuit of such a thin film magnetic head comprises a lower magnetic layer, an insulating film formed over the surface of the lower magnetic layer, a single or a plurality of superposed conductive coil layers formed on the insulating film, an insulating film formed over the conductive coil or conductive coils, and an upper magnetic layer formed over the insulating film.
Efforts have been made in the field of thin film magnetic heads in recent years for the reduction of track width and for the further improvement of the electromagnetic characteristics, particularly, the enhancement of recording and reproducing output of the thin film magnetic head to cope with the recent progressive reduction in track width of a recording medium. However, the thin film magnetic head has a large magnetic reluctance and is readily saturated magnetically because the sectional area of the magnetic thin film of the thin film magnetic head is smaller than that of a magnetic head of a bulk type. Magnetic saturation is liable to occur particularly in the magnetic gap section of the thin film magnetic head, having a particularly small sectional area. The magnetic saturation of the magnetic gap section increases the effective gap length in recording operation, reduces recording density and deteriorates the electromagnetic conversion characteristics. The saturation of the magnetic gap section of the thin film magnetic head may be obviated by increasing the thickness of the magnetic film to increase the sectional area of the core or by increasing the depth. However, it is difficult to form the magnetic film in a thickness large enough to obviate the saturation, and increase in the depth, which is effective for obviating the saturation though, deteriorates the overwrite characteristics.